Cation exchange materials for dialysis systems

Abstract

A sorbent cartridge device includes an ion-exchange material containing zirconium phosphate and no more than about 0.1 mg of leachable phosphate ions per about 1 g of the ion-exchange material. In one example, the cartridge also includes a phosphate-adsorbing material containing zirconium oxide. In this example, the weight ratio between zirconium phosphate and zirconium oxide in the cartridge is from about 10:1 to about 40:1. The zirconium phosphate may be alkaline zirconium phosphate prepared by a process including the following steps: (i) drying acid zirconium phosphate to obtain a dry acid zirconium phosphate; (ii) combining the dry acid zirconium phosphate with an aqueous solution to obtain an aqueous slurry; and (iii) combining the slurry with an alkali hydroxide to obtain the alkaline zirconium phosphate. During step (ii), any free phosphate ions in the dry acid zirconium phosphate leach out into the aqueous phase of the slurry.

What is claimed is: 
     
       1. A sorbent cartridge device, comprising:
 an ion-exchange material comprising zirconium phosphate, 
 wherein the device comprises less than about 0.1 mg of leachable phosphate ions per about 1 g of the ion-exchange material, and 
 weight ratio of P to Zr in the ion-exchange material is from about 1.5:1 to about 2:1. 
 
     
     
       2. The device of  claim 1 , comprising from about 0.01 mg to about 0.03 mg of leachable phosphate ions per about 1 g of the ion-exchange material. 
     
     
       3. The device of  claim 1 , further comprising a phosphate-adsorbing material comprising a zirconium oxide. 
     
     
       4. The device of  claim 3 , wherein the weight ratio between the zirconium phosphate and the zirconium oxide in the device is from about 10:1 to about 40:1. 
     
     
       5. The device of  claim 3 , comprising a homogenous mixture of the zirconium phosphate and the zirconium oxide. 
     
     
       6. The device of  claim 3 , comprising a layer of the zirconium phosphate and a layer of the zirconium oxide. 
     
     
       7. The device of  claim 1 , further comprising a urea-decomposing material. 
     
     
       8. The device of  claim 7 , wherein the urea-decomposing material is a urease enzyme. 
     
     
       9. The device of  claim 7 , further comprising alumina. 
     
     
       10. The device of  claim 1 , wherein the zirconium phosphate comprises an alkaline zirconium phosphate. 
     
     
       11. The device of  claim 10 , wherein the alkaline zirconium phosphate is prepared by a process comprising:
 drying an acid zirconium phosphate to obtain a dry acid zirconium phosphate; 
 combining the dry acid zirconium phosphate with an aqueous solution to obtain an aqueous slurry of the acid zirconium phosphate; and 
 combining the slurry with an alkali hydroxide to obtain the alkaline zirconium phosphate. 
 
     
     
       12. The device of  claim 1 , comprising:
 sodium content of about 60 mg to about 100 mg per about 1 g of the ion-exchange material; 
 ammonia or ammonium adsorption capacity of about 15 mg to about 20 mg per about 1 g of the ion-exchange material. 
 
     
     
       13. A dialysis system comprising:
 a dialysate generation machine; 
 a pump adapted to move fluid through the dialysate generation machine; and 
 a sorbent cartridge device fluidically connected to the dialysate generation machine, wherein 
 the device comprises an ion-exchange material comprising zirconium phosphate and less than about 0.1 mg of leachable phosphate ions per about 1 g of the ion-exchange material, wherein weight ratio of P to Zr in the ion-exchange material is from about 1.5:1 to about 2:1. 
 
     
     
       14. The system of  claim 13 , wherein the device comprises from about 0.01 mg to about 0.03 mg of leachable phosphate ions per about 1 g of the ion-exchange material. 
     
     
       15. The system of  claim 13 , wherein the device comprises a phosphate-adsorbing material comprising a zirconium oxide. 
     
     
       16. The system of  claim 15 , wherein the weight ratio between the zirconium phosphate and the zirconium oxide in the device is from about 10:1 to about 40:1. 
     
     
       17. The system of  claim 13 , wherein the device comprises a urea-decomposing material. 
     
     
       18. The system of  claim 13 , wherein the zirconium phosphate comprises an alkaline zirconium phosphate. 
     
     
       19. A method of removing one or more substances from a spent dialysis solution, the method comprising passing the spent dialysis solution through a sorbent cartridge device comprising an ion-exchange material comprising zirconium phosphate,
 wherein the device comprises less than about 0.1 mg of leachable phosphate ions per about 1 g of the ion-exchange material and wherein weight ratio of P to Zr in the ion-exchange material is from about 1.5:1 to about 2:1. 
 
     
     
       20. The method of  claim 19 , the one or more substances comprise ammonia or ammonium.